Thermal responsive switch



Feb. 24, 1925. 1,527,645

C. l'. HALL THERMAL RESPONSIVE SWITCH Filed Jan. 8. 1923 [27 van 60;".- Chester .7. //a//,

Patented Feb. 24, 1925.

UNITED STATES CHESTER I. HALL, 01' FORT WAYNE, INDIANA, ASSIGNOR COMPANY, A CORPORATION OF NEW TO GENERAL ELECTRIC YORK.

THERMAL RESPO'NSIVE SWITCH.

Application filed January 8, 1928. Serial No. 611,894.

To all whom it may concern.

Be it known that I, CHESTER I. HALL, a citizen of the United States, residin at Fort Wayne, in the county of Allen, tate of Indiana, have invented certain new and useful Improvements in Thermal Responsive Switches, of which the following is a specification.

My invention relates to improvements in thermal responsive switches and in particular to improvements in thermal responsive switches which are arranged toeffect the interruption of an electric circuit or in response to a sustained abnormal current. One of the objects of the invention is the provision of an improved switch of the character indicated which will take into account the heating efi'ect caused by the current taken by an electric translating device'which is protected by the switch so that the circuit to the translating device will be automatically and quickly opened when the current taken by the translating device is abnormally hi h and. which will eflect the opening of t e circuit to the translating device in case an ordinary overload has persisted for a definite interval of time.

Another object of the invention is the provision of a switch of the character indicated which shall have two cooperating switch members which jointly control an electric circuit and which are individually controlled in response to the heating efiect of the cur rent in respective conductors of a supply circuit for the translating device. whereby in case an .overload is carried for a predetermined time interml by either one or both of the conductors for the translating device, at least one of the switch members of the switch will be caused to open with a snap action and thereby efiect the opening of the circuit to the transmitting device. These and other objects of the invention, as will be either pointed out particularly hereinafter or as will. be apparent to those skilledin the art, are attained in the switch in the accompanying drawing, in which Fig. 1 1s a plan view of a double-pole switch accordance with the invention; Fig. 2 is a side view of the same; and Fig. 3 is a very sim lified diagram of a control system for an e ectric motor in which the switch of the invention is used to protect the motor. from conditions caused by overheating. Referring to the drawings, the electric switch therein shown as an embodiment of the invention comprises two relatively movable switch members 10 and 11 which are adapted to make engagement with each other at their respective contacts so as to complete an electric circuit through the switch contacts. The switch member 10 is secured to a block 12 of insulating material which has a pivotal connection with and is supported by the pivotally mounted adjusting member 13. The switch member 10 is biased to the open posit1on (out of engagement with the switch member 11) by means of the spring 14 which has one end connected with the post 15 whlch forms the pivotal connection between the adjusting member 13 and the block 12, and the other end of the spring is connected to the block 12, so that if unrestrained the switch member will assume the open position. In order to restrain the switch member in the closed position, the thermostatic latch 16 is provided. The free end of the latch is arranged to abut against the slider 17 which is secured to the block 12 which carries the switch member 10. The thermostatic latch 16 is heated in accordance with the current through one of the supply conductors of an electric translating device by means of the heating element 18 which is preferably although not necessarily, a strip of electric resistance material and which may be either directly included in one of the conductors of the supply circuit controlled by the electric switch or may be heated by a current proportional to the current in the conductor of the supply circuit, as will be understood by those skilled in the art.

The switch member 11 is carried by an insulatingblock 19which is similar to the insulating block 12 and this switch member is also biased out of engagement with the switch member 10 b means of the spring 20. A portion of the b ock 19 has been broken away to show the manner in which the switch members 10 and 11 may be adjusted so as to vary the settinJg of the thermal responsive switch. It will observed that the adjusting member 21 is pivotally mounted at 22 in the insulating base 23, and this member carries a pin 24 which is disposed between the pivot 22 and the end of the adjusting member. This pin 24 provides a pivotal connection for the switch member 11, and by reason of the fact that the pin is no i adjacent the pivotal support 22 and between cuit of the line contactor 39. With the parts the pivotal support and the end-of the adj usting member 21, by moving the adjusting member about its pivotal support, the slider 25, the block 19 and the switch member 11 will be moved up and down substantially tangentially with respect to the abutting free end of the thermostatic latch 26, the other end of which is secured in the terminal post 27. A relative movement is thus imparted to the latch and switch member and for the purpose of adjustment. Opposite the end of the adjusting member 21 is a scale 28 which gives a visual indication of the adjustment of the switch member 11, and a scale 29 is provided for giving a visual indication of the setting of the adjusting member 13 for the switch member 10. The construction and arranlgement of the adjusting device for the switch member 10 is identical with that previously described in con nection with the adjusting device for the switch member 11. The thermostatic latch 26 is arranged to be heated by the heater 30 which may either be included in one'of the conductors of an electric circuit or a translating device, or may be connected so that only a proportional part of the current in the supply circuit conductor passes through the heater.

A sin le device 31 is provided for cooperating with the insulating blocks 12 and 19 for manually reclosing the switch after it has been opened in response to the heating effect of the current in an electric circuit.

This resetting device may take various forms, and I have merely indicated one by way of illustration. In the arrangement shown in the drawing, the resetting device comprises a cross-bar 32 which is carried by a pin 33 which is resiliently held by the spring 34: in a position with respect to the support 35 so that the cross-bar 32 is out of engagement with the insulating blocks 12 and 19. By pressing on the button 36, the rod 33 may be moved against the action of v the spring 3& so as to thereby bring the cross-bar 32 into engagement with either one or both of the insulating blocks 12 and 19 so as to return the switch contacts 10 and 11 to their respective closed position.

Referring to Fig. 3, it will be seen that the translating device which is protected by means of my improved thermal responsive switch is shown as an alternating current motor 37, which is adapted to be connected to the three-phase source of supply 38 by means of the line contactor 39. The heater 30 is included in one of the supply conductors for the motor and the heater 18 is included in another of the supply conductors of the motor. The thermalresponsive switch is shown as in the closed circuit-completing position, and it will be observed that the switch contacts are included in the coil cir- "upon the nature of the unbalancing of in their respective positions shown in this drawing, in order to start the motor, the push button 40 will first be closed, thereby completing a circuit forthe coil of the line contactor through the start push button 40, the stop push button 41, coil of the line cont actor, switch contact members 10 and 11 to the middle of the supply conductorsof the three-phase source of supply. The line contactor will close and establish a maintaining circuit for its coil through the auxiliary switch 42 so that the start push button 40 may be released. In case the electric motor takes a predetermined overload for a predetermined interval of time, the thermostatic latches 26 and 16 will be fiexedupwardly out of engagement with their respective sliders 25 and 17 so that these switch members will be automatically released to open quickly in accordance with their bias, thereby giving the switch members and separating the switch contacts carried by the switch members 10 and 11 by a considerable distance a snap action to the opening ofand disrupting quickly any arcs which tend I to form at the thermal switch contacts. When the switch members 10 and 11 assume their respective open positions, the coil circuit of the line contactor 39 is deenergized and this contactor will open, thereby disconnecting the motor from the supply circuit and requiring automatically reset by pressing on the button 36 and the push button 40 must be closed prior to again connecting the motor to the source of supply. It will also be observed that in case there is a substantial unbalancing of the currents in the respective conduc-- tors of the supply circuit for the electric motor, the thermal responsive switch will protect the motor from conditions caused by overheating. Thus, either one of the thermostatic latches will operate, dependitrlllge currents in the respective supp-1y conductors, so that at least one of the switch members of the thermal responsive switch will be automatically released so as ance with its bias and thus effect the opening of the line contactor 39. It will also be observed that in case any one of the supply conductors is opened. the motor is protected from conditions caused by overheating when running single-phase. since at least one of the thermostatic latches will be effective to cause the opening of its respective switch member so as to thereby cause the opening of the line contactor It will he further observed that after the thermal responsive switch has operated, the circuit for the motor cannot be mantained completed until the thermostatic latch which 'efiected the opening of the circuit has cooled suflic1ently to engage with its respective slider. It w1ll that the thermal -switch be to open in accordalso be noticed that the thermal switch contacts 10 and 11 are given a wiping action in closing and in opening by reason of the inherent resiliency of the supports which car the engaging contact buttons so that the contacting surfaces are kept clean and smooth. Good electrical contact is thus secured and burning of the contacts is minimized.

In accordance with the provisions of the patent statutes, I have described the principle of operation of my invention, together with the apparatus which I now consider to represent the best embodiment thereof, but I desire to have it understood that the apparatus shown is only illustrative and that the invention can be carried out by other means.

IVhat I claim as new and desire to secure by Letters Patent of the United States, is,

in accordance with its bias, a pivotallv' 1. The combination in an electric switch of a switch member biased to the open position, a flexible thermostatic latch secured at one end with the free end thereof arranged to cooperate with the switch member to hold the same in the closed position, the said latch adapted to be flexed responsively to the heating effect of an electric current so that the free end of the latch releases the switch member to move to the open position the switch members in circuit closing engagement, means heated in accordance with the current of one conductor of a supply circuit for the translating device for eating one of said latches to release its corresponding switch member in accordance with the heating effect of the current in the said conductor, and means heated in accordance with the current in another conductor of the supply circuit for heating the other thermostatic latch to release its corresponding switch member in accordance with the heating eflect of the current in the other supply circuit conductor.

3. The combination in an electric switch for controlling a translating device, of a air of relatively movable switch members i-ased out of engagement with each other, a flexible'thermostatic latch for each switch member for holding the switch members in clrcuit closing engagement, means heated 1n accordance with the current 1n one conductor of a supply circuit for the translating device for heating one of said latches to cause the same to flex and release its corresponding switch member in response to the heating effect of the current in the said conductor, and'means heated in accordance with the current in another conductor of the supply circuit :tor heating the other thermostatic latch to cause the same to flex and release its corresponding switch member in response to the heating efiect of the current in the said other supply conductor.

4c. The combination in an electric switch for controlling a translating device, of a pair of switch members biased out of engagement with each other, a thermostatic latch for each switch member for holding the switch members in cireuitclosing position, means heated in accordance with the current in one conductor of a supply circuit .for the translating device for heating one of said latches to release its corresponding switch member in accordance with the heating of the current in the said conductor, means heated in accordance with the current in another conductor of the supply circuit for heating the other thermostatic latch to release its corresponding switch member in accordance with the heating effect of the current in the other supply conductor, and a single device cooperating with the said switch members for returning the switch members into engagement with each other.

5. The combination in an electric switch for controlling a translating device, of a pair of relatively movable switch members biased out of engagement with each other,

a separate flexible thermostatic latch for each switch member, each of said latches secured at one end with the free end thereof arranged to cooperate with its corresponding switch member to hold the same in the closed position, each of said latches adapted to be flexed responsively to the heating effect of the current in a separate conductor of a supply circuit for a translating device so that the free end of the latch releases its corresponding switch member to move to the open position in accordance with its bias, separate pivotal supports for the said switch members, separate adjusting members for individually shifting the said pivotal supports with respect to their corresponding thermostatic latches, and a single device adapted to cooperate with the said switch members for returning the same into engagement with each other.

In witness whereof, I have hereunto set my hand this 2 day of January, 1923.

CHESTER I. HALL. 

